Chelsea FC still need to strengthen a few more areas in the team, insists Tuchel.
Thomas Tuchel has been speaking to the media ahead of Chelsea FC's pre-season clash against Arsenal in the U.S, and the German pointed out that they need more new signings.
This comes after the Premier League club opened talks with LaLiga club Sevilla over defender Jules Kounde.
Reports in Spain say Chelsea have finally agreed a £55million deal for Jules Kounde as the west London club edge closer to sealing their third major transfer.
The Blues have recruited Raheem Sterling and Kalidou Koulibaly from Manchester City and Napoli respectively this summer but Tuchel is eager to add another centre-back to his squad having lost Antonio Rudiger and Andreas Christensen to Real Madrid and Barcelona this summer.
"We need a couple more to improve the squad," Tuchel said. "We finished third last season - there was a gap. If you want to keep your position you need to improve. You can never stand still. Other teams will overtake you. We've lost players.
"This is common sense. It's the dream of every manager to find players from your own league who can adapt so easily. Raheem knows the habits of English clubs and has English teammates here.
"Kalidou (Koulibaly) knows Mendy from the national team and Jorginho was a big help from Napoli to make the process of integration faster. They are huge players for us. We need to speed things up."
Chelsea were keen to land defender Matias De Ligt, but the Dutchman has decided to join Bayern Munich for a reported fee of £68m.